Automated machines for opening large quantities of envelopes are known, such as those machines disclosed in U. S. Pat. Nos. 4,124,968; 4,353,197; and 4,863,037, issued to the assignee of the present application, all of which are incorporated herein by reference. Such machines may be broadly classified by two types, one type in which the envelope is severed along at least one edge and then spread open to allow manual removal of the contents, and a second type in which the envelope is opened and the contents thereof extracted automatically.
FIG. 1 shows a typical prior art apparatus 10 for facilitating the manual extraction of contents from a large quantity of envelopes. A quantity of envelopes 12 are retained in a bin 14. One at a time, the envelopes 12 are removed from bin 14 by suction cup 16, which alternately extends into engagement with the nearest envelope in the bin, and retracts back into sloping shelf 18, carrying the envelope with it. Each envelope is then indexed by conveyor belts 20 along shelf 18 toward the upper right in FIG. 1, passing through cutter 13, which slits the topmost edge of each envelope, thereby opening the envelope. The belts are stopped when the opened envelope reaches a position between suction cups 22, 23. The suction cups 22, 23 are first moved toward each other until they engage the sides (faces) of the envelope, and are then moved apart, thereby spreading the sides of the envelope open. An envelope with its sides spread open is shown at 25 in FIG. 1. This spreading open of the envelope is designed to facilitate the extraction of any contents which may be present in the envelope by an operator positioned alongside shelf 26. To this end, all that is necessary is for the operator to reach into the spread open envelope 25 to extract its contents.
One of the most crucial considerations for fast and efficient extraction of the contents from a large quantity of envelopes is ascertaining that envelopes passing through the system are in fact emptied of all their contents. Whether the contents of the envelope are extracted directly by an operator's hand or by other means, there will always be a possibility that some of the contents of the envelope, such as a check or an important document, will remain stuck to one side of the envelope even when the opposite faces of the envelope are spread apart. In some envelopes, the contents may have been inserted folded, and others not. In some envelopes, the contents may be bunched to one side, rather than neatly centered within the envelope. These and many other variations in content configuration can occur even when all of the envelopes being processed are supposed to have identical contents.
Obviously, the accidental discarding of checks must be avoided. Even the loss of documents, such as copies of invoices which accompany the checks, is clearly undesirable. For a recipient of a large quantity of checks, such as a utility or a credit card company, the resulting confusion and delay in document processing can be expensive. Simultaneously, it is desirable to extract checks from envelopes as quickly as possible, while avoiding such errors. When a company receives a large quantity of checks, a delay of even a few hours in depositing the checks may result in a significant loss of interest income.
Machines in common use for opening envelopes and facilitating the extraction of their contents are capable of operating at extremely high speeds. Even for those machines which operate to spread the sides of the envelope apart to allow manual extraction of the contents, typical operating speeds may reach up to 2,400 envelopes per hour, or one envelope every 1.5 seconds. This gives rise to the corresponding need to ensure complete extraction of all contents without significantly interfering with the speed of the operation.
Commonly-used techniques for verifying that envelopes have been completely emptied operate on the principle of the transmissivity of radiant energy, such as visible light, infrared light, or sound, through the envelope and any contents therein. These techniques extend to two types of system operation, candling and content-activation. In the apparatus shown in FIG. 1, photocell 30 and light source 32 together form a candling apparatus, while light sources 33 and 34 interact with photocells 35 and 36, respectively, to form a content-activation apparatus. The content-activation apparatus operates at the extraction station with suction cups 22 and 23, while the candling apparatus, is disposed downstream in the path of the envelopes to inspect the envelopes after the contents have been removed.
In general principle, an empty envelope will allow a certain threshold quantity of light to pass through to the photocell, while an envelope having documents remaining therein will allow a lesser quantity of light to pass through to the photocell. This lesser light transmissivity of an envelope still containing a document or documents is used to signal, through a control system, that the envelope then passing by the photocell still contains documents. In a candling procedure, the envelope is flagged for special handling, e.g., manual removal of whatever remains in the envelope. In a content-activation procedure, the envelope is retained at the extraction station, since it is not yet ready for discarding.
FIG. 2 is a simplified view of the content-activation system used in the apparatus of FIG. 1. Lamps 33 and 34 direct light, at 41 and 42 respectively, through different points of a spread-open envelope 25. Light passing through the envelope is then accepted by photocells 35 and 36. Photocells 35 and 36 are in turn operatively connected to a belt drive control circuit 38 which operates a motor 40 for causing motion of the envelopes passing along the shelf 18. Two sets of lamps and photocells are used to compensate for potential irregular positioning of contents within the envelopes which are being processed for extraction. Photocells 35 and 36 interact with belt drive control circuit 38 in such a way that, when a sufficient quantity of light passes from the lamps 33 and 34 through envelope 25 to the photocells 35 and 36, the belt drive control circuit will cause the motor 40 to index the envelope 25 toward the candling apparatus 30 and 32, while simultaneously removing another of the envelopes 12 from the stack and moving it to the extraction station. In the apparatus of FIG. 1, the candling apparatus then act as a second check for contents remaining in the envelope 24, before it is discarded. If the candling apparatus detects any remaining items in the envelope 24, the apparatus will indicate that not all of the contents have been extracted, and will generally discontinue further tranport of the envelope so that the remaining contents may be extracted.
Candling and content-activation techniques generally operate on a principle of a fixed threshold value of light transmissivity (indicating an empty envelope). When the intensity of the light passing through an envelope is above the threshold value, the envelope is deemed empty, and when this intensity is below the threshold value, the envelope is deemed to be not empty. As a result, the effectiveness of the apparatus is highly dependent on the exact value of the threshold in relation to the characteristics of the envelope being subjected to extraction. The prior art apparatus shown in FIGS. 1 and 2 therefore includes an external knob 37 operating a potentiometer 39 which controls the threshold value of light transmissivity to be detected by the belt drive control circuit 38. In practice, however, it has been found that such techniques can be further improved. For example, in the context of automated extraction machines, a crucial factor affecting the efficiency of the operation is the variation in transmissivity caused by the spreading apart of the side of the envelope, as with the envelope 25 in FIG. 1. Such spreading apart of the envelope causes a significant variation and distortion of the observed transmissivity of the envelope, which very often results in a misreading of whether the envelope has been emptied of all its contents. This problem is one of the primary sources of error in prior art content-activation systems. No matter how carefully a threshold value is selected for identifying an empty envelope, there will nevertheless tend to be some error because a spread-open envelope which is actually empty may be observed to transmit less light than an envelope still having contents therein.